The invention relates to a folder equipped with means for making a smooth cut and comprising two knife cylinders fitted with shear cut knives, of which one is provided with pins for piercing the paper near the shear knives in order to hold paper trimmings and is provided with a suction duct to act on part of its circumference.
A folder of this type is for instance described in the German patent 3,030,706. In such arrangements irregular operation may be caused by the stripping of the trimmings from the pins not being sufficiently reliable in the suction duct. The consequence of this is that a pile of trimmings accumulates on the pins and the lower trimmings are pushed onto the pins again and again.
Although to provide a remedy it would be possible to increase the level of vacuum in the suction duct, this would lead to an excessively intense air current surrounding suction duct and thus cause interference with folded products running through the folder. Furthermore, owing to such and air current an excessive noise level would be probable, quite apart from the added complexity of the folder.
It would also be conceivable to provide mechanical lifting means on the knife cylinder to act on the trimmings on the pins and to reliably clear them from the pins. The lifting means would however entail the provision of comparatively large cylinder wells. Particularly in the case of cylinders with a small diameter such wells would be prone to very much weaken the cylinder and cause it to be insufficiently robust.